We are all, to varying degrees, fascinated by the practice of medicine because of its curious combination of dispassionate abstraction and extreme human emotion. Few other professions demand of its practitioners the objective application of science at the point where the human condition is presented at its most vulnerable, those terrifying moments when the body that we took for granted is suddenly revealed to be a precarious scaffold of skin and bone. In those moments, we expect our doctors and surgeons to be reassuringly omniscient and simultaneously caring, to be able to empathise while maintaining the necessary distance of rationality. We want them to possess the power of the divine while remaining consolingly human.

Gabriel Weston explores this intriguing conundrum in her compelling semi-fictionalised memoir, Direct Red. At several points, she questions how far she should allow the expression of her human response to a patient in distress - how, for instance, should she tell a young man at the peak of his physical fitness that he has a terminal tumour wrapped around his sigmoid colon? How should she respond when the handsome survivor of a motorbike accident, with whom she has built up a closeness that in other circumstances would lead to romantic entanglement, invites her into his bed at night? How to comfort a dying child when, working the frantic, non-stop hours of an on-call junior doctor, she has an insurmountable desire simply to return to bed?

For Weston, there is an additional subtlety nestling at the heart of these questions. As a woman, those she treats expect her to possess a comforting maternalism lacking in her male counterparts. And yet, as a junior doctor trying to make her mark in a predominantly male sphere, she finds herself pressured to overcompensate, to prove beyond doubt that she is capable of exercising the detached judgment of a clinician whose primary focus is cure, not compassion.

When Weston encounters Mrs McNamara, a middle-aged woman suffering from mouth cancer, she knows on the one hand that "the cancer colonising this woman's mouth must be unbearably painful". But as a registrar who is new to the speciality of head and neck surgery, Weston is also keen to impress her superiors and increase her surgery hours by performing a challenging operation.

"Alongside this sense of empathy jostle other heartier emotions: excitement, anticipation, something like a miniature version of pride," she writes. And later: "Roughness is an absolute requirement of a surgeon... we have to subdue humanity every time we stick the knife in."

The conflict between these opposing forces - personal and professional, female and male, patient and physician, pain and relief - makes Direct Red extraordinarily gripping, in spite of there being none of the usual narrative devices: there are no consistent plot lines, no recognisable heroes and no unexpected denouements. Instead, Weston has arranged her writing into thematic sections, a series of short parables, each designed to illuminate a particular aspect of her craft, among them "Death", "Beauty" and "Ambition".

Some of the most interesting writing comes not from the interaction between doctor and patient, but from the tensions that exist between the surgeons themselves. It seems that the uneasy alliances and trivial etiquettes of office politics exist even when the work is a matter of life and death. I didn't know whether to be reassured by this twinge of recognition for human foibles in the operating theatre or profoundly depressed, but it opened a new aspect to the surgical experience that I had never imagined, despite being a surgeon's daughter.

On one occasion, Weston is so driven by a desire to impress a talented boss by the speed of her surgery that she inadvertantly cuts an artery, gushing blood over the theatre. On another, she is seized by the fear that her uncertain diagnosis of a blocked airway will prove groundless and that the surgery she has recommended will simply highlight her incompetence. "My only prayer was that Mr Charles should be in real trouble, about to die, even," she writes with black humour. "Anything but OK. Let his airway be sick, I thought."

Direct Red is a curiously thrilling read, written with an elegance of expression heightened by both its clarity and economy. Weston slices into sentences with scalpel-like precision. Her first memory of surgery is described as a sensory experience: "The mixed aroma of clean, hard surfaces and the loam of the body's upturned soils." The accident and emergency department, with its habitual mixture of the drunk and the desperate, embodies "the strip-lit awfulness of life gone wrong".

I can't remember reading a book that absorbed me so completely, that was so riveting and yet so exact, that so cherished the beauty of language even when using it to convey the ugliest extremes of disease. It is frequently said that doctors have incredibly bad handwriting. I'm not sure what Gabriel Weston's prescription forms read like, but if this book is anything to go by, she more than compensates for any illegibility by the dazzling quality of her content.